1. Field of the Invention
The present invention relates to a rolling bearing apparatus including a bearing portion and a lubrication unit that supplies a slight amount of lubricant to the bearing portion.
2. Description of Related Art
Rolling bearings are used, for example, as spindle bearings of machine tools. As shown in FIG. 4, a housing 90 of a spindle unit of a machine tool houses a plurality of rolling bearings 91 provided along an axial direction. The spindle unit shown in FIG. 4 uses oil-air lubrication to ensure appropriate lubrication of the rolling bearings 91. However, the oil-air lubrication involves high running costs due to air consumption. In addition, the oil-air lubrication needs incidental facilities such as an oil-air supply apparatus and an air clean unit, possibly leading to high facility costs.
As another means for lubricating the rolling bearings 91, a rolling bearing apparatus (hereinafter, referred to as the bearing apparatus) incorporating a lubrication unit described, for example, in Japanese Patent Application Publication No. 2004-108388 (JP 2004-108388 A) is known. In this bearing apparatus, the lubrication unit is installed on an inner periphery of an outer ring of a rolling bearing. The rolling bearing (bearing portion) and the lubrication unit are integrated together. The lubrication unit includes a tank, a pump, and so forth. The tank stores lubricant. The pump discharges the lubricant in the tank into an annular space between an inner ring and the outer ring.
By using the bearing apparatus described in JP 2004-108388 A instead of the rolling bearings 91 of the spindle unit of the machine tool shown in FIG. 4, it is possible to overcome the problem of costs attributable to the oil-air lubrication.
However, the bearing apparatus having the lubrication unit is housed in the housing 90 and the lubrication unit contains the tank storing the lubricant. Thus, when maintenance is performed to refill the tank with the lubricant, the spindle unit as shown in FIG. 4 is required to be disassembled to take out the bearing apparatus from the housing 90. This may take a longer time for the maintenance, adversely affecting productivity.